1. Field of the Invention
This invention relates to an improved apparatus and method for braiding fine denier yarns into sutures for surgical applications.
2. Description of the Prior Art
Braided products and apparatus for production of such products are well-known. However, for some time now, braiding machines have been directed to production of braided products of relatively bulky sizes for uses in applications in packaging, window blind pulls, braided rope or the like. In essence, the applications for such braided products are legion.
Typical of the braiding mechanisms used for such products are disclosed in U.S. Pat. Nos. 776,842 to Horwood, 1,154,964 to Bentley, 1,285,451 to Stanton, 1,358,173 to Penso et al., 1,486,527 to Larkin, 1,785,683 to Mallory, 2,079,836 to Brown et al., 2,200,323 to Barrans et al., 2,452,136 to Marti, 4,158,984 to Griffiths, 4,304,169 to Cimprich et al., 4,333,380 to Kozlowski, 4,716,807 to Fischer, 4,753,149 to Celani, 4,909,127 to Skelton et al. and 4,922,798 to Ivsan. British Patent Publication No. 138,069 dated Sep. 2, 1920 relates to improvements in such braiding devices.
Sutures intended for the repair of body tissues must meet certain requirements: they must be substantially non-toxic, capable of being readily sterilized, they must have good tensile strength and have acceptable knot-tying and knot-holding characteristics and if the sutures are of the bio-absorbable variety, the bio-absorption of the suture must be closely controlled.
Sutures have been constructed from a wide variety of materials including surgical gut, silk, cotton, polyolefins such as polypropylene, polyamides, polyesters such as polyethylene terephthalate, polyglycolic acid, glycolide-lactide copolymer, etc. Although the optimum structure of a suture is that of a monofilament, since certain materials of construction would provide a stiff monofilament suture lacking acceptable knot-tying and knot-holding properties, sutures manufactured from such materials have been provided as braided structures. Thus, for example, sutures manufactured from silk, polyamide, polyester and bio-absorbable glycolide-lactide copolymer are usually provided as multifilament braids.
Currently available braided suture products are braided on conventional braider-carriers which travel around the perimeter of the braider deck to result in a tubular type braid with the yarns crossing over each other on the surface of the braid. In the larger sizes, e.g., 5/0 and larger, the tubular braid, or sheath, is constructed about a core structure which is fed through the center of the braider. Known tubular braided sutures, including those possessing cores, are disclosed, e.g., in U.S. Pat. Nos. 3,187,752; 3,565,077; 4,014,973; 4,043,344; and, 4,047,533.
High speed production of braided sutures from fine denier yarns presents difficulties not encountered in connection with production of heavy duty braided products such as cord, rope or the like. In particular, it has been found that typical braiding mechanisms abrade, damage or break the fine denier filaments used to make braided suture products, and reduce product yield. Moreover, many braided suture products, particularly absorbable braided sutures, are stiff and wiry and exhibit "memory" or "sets". Recent attempts to improve the flexibility, hand and tissue drag characteristics of braided sutures have resulted in new braid structures possessing a significantly greater number of sheath yarns for a given overall denier, the sheath yarns being fabricated from individual filaments of finer denier than filaments which are typical of known types of braided sutures. Braided sutures of this type are disclosed and claimed in U.S. patent application Ser. No. 491,215 filed Mar. 9, 1990, now U.S. Pat. No. 5,019,093, and prior related applications. While it is possible to produce such structures on conventional braiders, applicants were able to do so at a maximum production rates approaching only about 6 meters per hour.
The present invention relates to improvements in such apparatus and methods for continuously braiding fine denier yarns into fine braided products having predetermined construction and appearance suitable for use in body tissue repair. More specifically, the present invention makes it now possible to produce the preferred braided sutures at relatively high speeds on the order of about 13 to 15 meters per hour.